| In recent years, GPS navigation systems have found widespread use in many diverse applications. The achievements of GPS navigation systems in positioning and navigation services have been nothing short of extraordinary. With the use of carrier phase measurements and Differential GPS (DGPS), centimeter-level performance is achievable today. Therefore, the principal issues for modern navigation are not related to accuracy per se, but robustness. Unfortunately in this regard, all radionavigation systems are subject to Radio Frequency Interference (RFI). In response, this research is focused on the development of interference-robust navigation systems for aviation applications.;A new dual-frequency Carrier-phase DGPS (CDGPS) architecture has been developed in this research and its performance was evaluated relative to the requirements for a unique shipboard landing application. RFI vulnerability was addressed for this application by directly incorporating a single frequency architecture as a back-up in the event of hostile jamming on one frequency.;For critical civil aviation applications without access to dual frequency GPS signals, a novel method for tightly-coupling GPS and Inertial Navigation Sensors (INS) was developed to address the signal vulnerability issue. The new hybrid navigation system, based on the direct fusion of GPS and INS using state dynamics, is a mathematically rigorous approach, yet it is more direct and simpler to implement than existing GPS/INS integration schemes. The hybrid navigation system was validated with flight data, and predicted system performance was evaluated using a covariance analysis method. Necessary conditions on INS sensor and gravity model quality were derived to ensure that the hybrid system performance is compliant with navigation requirements for aircraft precision approach and landing.;In addition, a new fault detection algorithm, based on integrated Kalman filter innovations, was developed and evaluated against other existing GPS fault detection methods and radar altimeter detection technique. It is shown that the new algorithm outperforms existing methods in the detection of slowly developing ranging errors, such as those caused by ionospheric and tropospheric anomalies. It is also demonstrated that the radar detection technique can provide a significant benefit to navigation system integrity. |
